eslint/lib/rules/no-extra-label.js

   1 /**
   2  * @fileoverview Rule to disallow unnecessary labels
   3  * @author Toru Nagashima
   4  */
   5
   6 "use strict";
   7
   8 //------------------------------------------------------------------------------
   9 // Requirements
  10 //------------------------------------------------------------------------------
  11
  12 const astUtils = require("./utils/ast-utils");
  13
  14 //------------------------------------------------------------------------------
  15 // Rule Definition
  16 //------------------------------------------------------------------------------
  17
  18 module.exports = {
  19     meta: {
  20         type: "suggestion",
  21
  22         docs: {
  23             description: "disallow unnecessary labels",
  24             recommended: false,
  25             url: "https://eslint.org/docs/rules/no-extra-label"
  26         },
  27
  28         schema: [],
  29         fixable: "code",
  30
  31         messages: {
  32             unexpected: "This label '{{name}}' is unnecessary."
  33         }
  34     },
  35
  36     create(context) {
  37         const sourceCode = context.getSourceCode();
  38         let scopeInfo = null;
  39
  40         /**
  41          * Creates a new scope with a breakable statement.
  42          * @param {ASTNode} node A node to create. This is a BreakableStatement.
  43          * @returns {void}
  44          */
  45         function enterBreakableStatement(node) {
  46             scopeInfo = {
  47                 label: node.parent.type === "LabeledStatement" ? node.parent.label : null,
  48                 breakable: true,
  49                 upper: scopeInfo
  50             };
  51         }
  52
  53         /**
  54          * Removes the top scope of the stack.
  55          * @returns {void}
  56          */
  57         function exitBreakableStatement() {
  58             scopeInfo = scopeInfo.upper;
  59         }
  60
  61         /**
  62          * Creates a new scope with a labeled statement.
  63          *
  64          * This ignores it if the body is a breakable statement.
  65          * In this case it's handled in the `enterBreakableStatement` function.
  66          * @param {ASTNode} node A node to create. This is a LabeledStatement.
  67          * @returns {void}
  68          */
  69         function enterLabeledStatement(node) {
  70             if (!astUtils.isBreakableStatement(node.body)) {
  71                 scopeInfo = {
  72                     label: node.label,
  73                     breakable: false,
  74                     upper: scopeInfo
  75                 };
  76             }
  77         }
  78
  79         /**
  80          * Removes the top scope of the stack.
  81          *
  82          * This ignores it if the body is a breakable statement.
  83          * In this case it's handled in the `exitBreakableStatement` function.
  84          * @param {ASTNode} node A node. This is a LabeledStatement.
  85          * @returns {void}
  86          */
  87         function exitLabeledStatement(node) {
  88             if (!astUtils.isBreakableStatement(node.body)) {
  89                 scopeInfo = scopeInfo.upper;
  90             }
  91         }
  92
  93         /**
  94          * Reports a given control node if it's unnecessary.
  95          * @param {ASTNode} node A node. This is a BreakStatement or a
  96          *      ContinueStatement.
  97          * @returns {void}
  98          */
  99         function reportIfUnnecessary(node) {
 100             if (!node.label) {
 101                 return;
 102             }
 103
 104             const labelNode = node.label;
 105
 106             for (let info = scopeInfo; info !== null; info = info.upper) {
 107                 if (info.breakable || info.label && info.label.name === labelNode.name) {
 108                     if (info.breakable && info.label && info.label.name === labelNode.name) {
 109                         context.report({
 110                             node: labelNode,
 111                             messageId: "unexpected",
 112                             data: labelNode,
 113                             fix(fixer) {
 114                                 const breakOrContinueToken = sourceCode.getFirstToken(node);
 115
 116                                 if (sourceCode.commentsExistBetween(breakOrContinueToken, labelNode)) {
 117                                     return null;
 118                                 }
 119
 120                                 return fixer.removeRange([breakOrContinueToken.range[1], labelNode.range[1]]);
 121                             }
 122                         });
 123                     }
 124                     return;
 125                 }
 126             }
 127         }
 128
 129         return {
 130             WhileStatement: enterBreakableStatement,
 131             "WhileStatement:exit": exitBreakableStatement,
 132             DoWhileStatement: enterBreakableStatement,
 133             "DoWhileStatement:exit": exitBreakableStatement,
 134             ForStatement: enterBreakableStatement,
 135             "ForStatement:exit": exitBreakableStatement,
 136             ForInStatement: enterBreakableStatement,
 137             "ForInStatement:exit": exitBreakableStatement,
 138             ForOfStatement: enterBreakableStatement,
 139             "ForOfStatement:exit": exitBreakableStatement,
 140             SwitchStatement: enterBreakableStatement,
 141             "SwitchStatement:exit": exitBreakableStatement,
 142             LabeledStatement: enterLabeledStatement,
 143             "LabeledStatement:exit": exitLabeledStatement,
 144             BreakStatement: reportIfUnnecessary,
 145             ContinueStatement: reportIfUnnecessary
 146         };
 147     }
 148 };